Coordinated Health


Primary thrombocythemia is when the bone marrow is making too many platelets without a known cause. Platelets are needed for blood clotting.

Alternative Names

Essential thrombocythemia; Essential thrombocytosis

Causes, incidence, and risk factors

Primary thrombocythemia is caused by too much growth of a type of cell that is used to make blood cells. The platelets are mostly affected, but the red blood cells and white blood cells may be involved as well. This condition slowly gets worse over time. Because these platelets do not work normally, bleeding is a common problem.

The disease is part of a group of conditions known myeloproliferative disorders. Others include:

  • Chronic myelogenous leukemia
  • Polycythemia vera
  • Primary myelofibrosis

Most of the time, this condition affects people in middle age. It is also seen in younger people especially women under age 40.


  • Bleeding from the gastrointestinal tract, respiratory system, urinary tract, or skin
  • Bleeding from the gums
  • Bleeding (prolonged) from surgical procedures or tooth removal
  • Dizziness and headaches
  • Easy bruising and nosebleeds (epistaxis)
  • Numbness of the hands or feet
  • Ulcers on the fingers or toes

The condition may even cause strokes in some people.

Signs and tests

Most of the time, this condition if found through blood tests done for other conditions before symptoms appear.

Your health care provider will do a  physical exam to look for an enlarged spleen or liver. You may also have abnormal blood flow in the toes or feet that causes skin damage in these areas.

Other tests may include:

  • Bone marrow aspiration and biopsy
  • CBC
  • Genetic tests (to look for a change in the JAK2 gene)
  • Uric acid level


The doctors can do a procedure to remove platelets directly from the blood if you have life-threatening complications.

Long-term, you will need to take medicines to decrease the platelet count  and avoid complications. The most common of these medicines are hydroxyurea, interferon-alpha, or anagrelide. In some people with a JAK2 mutation, specific inhibitors of the JAK2 protein may be used.

In people who are at high risk for clotting aspirin at a low dose (81 to 100 mg per day) decreases clotting episodes.  Patients who may benefit from this treatment include older patients, and people with very high platelet levels or who have had past clotting episodes).

Many people do not need any treatment. However, the health care provider should monitor your condition.

Expectations (prognosis)

The outcome varies. Most people go for long periods without complications and have a normal lifespan. Complications from bleeding and blood clots can cause serious problems in a small number of people.

Rarely, the disease will change into acute leukemia or myelofibrosis.


  • Acute leukemia or myelofibrosis
  • Severe bleeding (hemorrhage)
  • Thrombotic episodes (stroke, heart attack, or blood clots in the hands or feet)

Calling your health care provider

Call your health care provider if:

  • You have unexplained bleeding that continues longer than it should.
  • You notice chest pain, leg pain, confusion, weakness, numbness, or other new symptoms.